Polarized reed relay wherein the permanent magnet is around the reed switch and in contact with the coil



sept. 3, 196s T. DE PARRY 3,400,348

ROLARIZED REED RELAY WHEREIN THE PERMANENT MAGNET IS AROUND THE REEDSWITCH AND IN CONTACT WITH THE COIL Filed July 5, 1961 /EXTERNAL CIRCUITFIG. 3A FIG. 3B

INVENTOR.

THEODORE DE PARRY ATTY United States Patent 3,400,348 POLARIZED REEDRELAY WHEREIN THE PERMA- NENT MAGNET IS AROUND THE REED SWITCH AND INCONTACT WITH THE COIL Theodore De Parry, Elmhurst, Ill., assignor toAutomatic Electric Laboratories, Inc., Northlake, Ill'., a `corporationof Delaware t Filed July 3, 1961, Ser. No. 121,534 3 Claims. (Cl.335-153) This invention relates to relays, and more Particularly, toencapsulated polarized'dry reed relays.

Prior art relays of the above type typically use permanent magnets tomaintain the reeds closed without the use of a continuous hold current.Normally these permanent magnets are attached to one or more of thecontacts reeds inside of a sealed capsule. While the use of a permanentmagnet inside of the glass capsule has successfully'solved theparticular problem of maintaining the contact reeds closed without theneed for continuous current through the energizing coil, a number ofother problems have thereby been introduced in the design in the use ofthis type of reed relay. For instance, the incorporation of a permanentmagnet or magnets inside of the glass capsule has materially increasedthe manufacturing cost and diiiiculties of constructing these reedrelays. It also causes the reed relay to be appreciably larger than thereed relays which do not contain the permanent magnet. 4In addition, theincorporation of permanent magnets inside of the encapsulated relay is amajor souree'of contamination of the vacuum. This results incontamination of the contact surfaces and thusmaterially effects thecontact reliability and also materially increases contact microphonicnoise generation.

Another :solution to the problem of maintaining the contact springsclosed without the need for continuous current passage through theenergizing coil has beenthe use of a permanent magnet positioned outsideof the glass capsule containing the magnetic contact reeds. The reedrelay so far invented utilizing this technique for maintaining thecontact reeds closed have a, number of disadvantages and `difiicultiesinherent in the design. For instance, the reed relays of this type haveresulted in rather large structures with permanent magnets whose shapeare extremely difficult to fabricate or manufacture. This of course hasincreased the manufacturing cost of the reed relay. In other reed relaydesigns wherein a permanent magnet of relatively simple shape have beenutilized to maintain the magnetic contact reeds close, otherdifficulties and disadvantages have accrued. For instance, in thesedesigns the use of multiple contact reeds, that is,

[three or more contact reeds, is essential to avoid completing circuitsin which eddy currents can flow. In addition, it is necessary tocarefully electrically insulate the permanent magnets from the contactsprings to insure that the contact springs are not shorted out.

The reed relay of this invention is of the type wherein a permanentmagnet holding the reeds in a closed condition without the use of acontinuous current passage through the energizing coil is locatedoutside of the glass tube.

Accordingly, an object of the invention is to provide a polarized dryreed relay whose cost of manufacture is minimized as a result of asimplified design.

Another object of the invention is to provide a dry reed relay whichoperates with a minimal energy signal.

Patented Sept. 3, 1968 ice Another object of the invention is to providea polarized diy reed relay wherein eddy current generation is minimized.

lStill another object of the invention is to provide a polarized `dryreedrelay which is substantially not affected by external magneticfields.

To accomplish these objectives the relay features in a general way: adry reed switch capsule which supports on the external surface thereof atubular-shaped permanent magnet which is placed coaxially over thecapsule and which is made of plastic magnetic material, and anenergizing coil which is in turn Wound on this permanent magnet.

These and other objects and features of the invention will be more"clearly understood from the following detailed description taken inconjunction with the drawings of which:

FIG. 1 is a cut vaway perspective view of a relay in accordance with theteachings of a first modification of the invention.

FIG. 2. is a cross sectioned side elevational view of a secondmodification of the invention.

FIG. 3a 4discloses a schematic of the magnetic circuit of the relay whenthe energizing current is of one polarity and,

FIG. 3b discloses a schematic of the magnetic circuit of the relay whenthe energizing current is of the reverse polarity. y

The relay as shown in FIG. 1 consists of; a pair of iiexible contactreeds 11 and 12 which are made of magnetic material, a hermetic vitreoustube 15 which is filled with an inert gas such as nitrogen, a permanentmagnet 14 which is made of plastic magnetic material, and an energizingcoil 13.

More specifically, reeds 11 and 12, constituting the magnetic armatureand core for the relay, extend'from opposite ends of gas filled vitreoustube 15, one end of each reed being within the tube and the other end ofeach reed `being external of the tube. The latter ends 12a and 11a serveas connecting terminals for the corresponding external circuit beingcontrolled by operation of the reeds. On the other hand, the ends Withinthe tube 11b and 12b respectively, are the longer of the two ends andare arranged so as to be in an overlapped and normally spaced apartrelationship with each other. Accordingly, the contact area is limitedto the overlapped portion of the two reeds. In applications whereoptimum contact operation is desired the contact area may be gold platedor gold diffused by conventional means. This technique reduces contactresistance between contact surfaces 116 and 126 to an absolute minimumand also minimizes corrosion.

The material from lwhich the reeds are constructed must possess certainphysical characteristics for proper mechanical closure of the reeds atthe contact areas 11b and 12b. These characteristics include lightweight to increase the sensitivity of the relay; special rigidity toinsure that the contacts do not bounce or close the contacts uponvibration of the relay; a high degree 0f resiliency to insure thatproper contact pressure is obtained between the contact lareas 11b and12b; and in addition, high fatigue strength so that the reed relay maybe in service for millions of operations. p

Permanent magnet 14 is tubular-shaped and is coaxially l A003418 s 4placed over the vitreous tube 15. The inside diameter of the ma-gnet 14should be only slightly greater than t-he outside diameter of vitreoustube so that it may be slipped over the tube during manufacture of therelay yet maintain a tight or snug lit with the tube.

Permanent magnet 14 is preferably constructed out of a plastic magneticmaterial. This material is rubber bonded and of magnetic-ferritecomposition. This material has a number of important characteristicswhich make it particularly suitable for application in reed relays ofthis invention. `One of its characteristics is that permanent magnetsconstructed from this material have exceptionally high coercivity andthus have a strong resist- -ance to dre-magnetization. In addition, themagnetization characteristics for this material produce essentially asquare hysteresis curve. Another important characteristic of thismaterial is the facility with which it may be machined or otherwiseshaped. This results in great economy in manufacturing productsutilizing this material.

Since in this material magnetic particles are bonded together by aninsulating media, such as rubber or plastic, the material has anextremely high resistivity. This characteristic is extremely importantin the operation of the high speed reed relay of this invention as willbe discussed subsequently. In fact, the absence of this characteristichas prevented the construction of similar designs in the prior art. Inaddition this plastic magnetic material is of a very light weight whichallows the product utilizing this material to also be of less weightthan if the magnet were constructed from conventional cobaltnickel orsteel magnets.

The magnetization of magnet 14 is such that the opposite poles are atthe two end faces 17 and 18. Thus, the flux lines are directed generallyin a longitudinal pattern over the tube 15. Around t-he magnet is anenergizing coil 13 which activates a change in the relationship of thereeds 11 and 12 and thus operates the external circuit.

By way of example, a second modication of the invention may be las shownin FIG. 2. This modification displays substantially the same features asthe lfirst modiication shown in FIG. 1 except for the additional featureof a plurality of pairs of reeds which are connected to a larger numberof external circuits. The reeds are positioned 'within a correspondinglarger hermetically sealed vitreous tube 30 which accordingly supports alarger permanent magnet 31 and energizing coil 32.

The operation of the relay Iwill now be described making reference toFIGS. l, 3a and 3b. With the contacts 11b and 12b open and no currentflowing through coil 13, the magnetic field set up by permanent magnet14 is axially through the vitreous tube. This magnetic field must not besufficient at the air gap between contacts 11b and 12b to cause them toclose. However, when 'an actuating current is passed through coil 13 inthe direction to set up a magnetic field which aids the magnetic fieldof the permanent magnet 14 reeds 11 and 12 will close due to themagnetic force exerted by the two magnetic fields on the flexible reeds.The magnetic eld set up by the passage of current through coil 13 alsocauses the state of magnetism in the permanent magnet to reach itsmaximum full strength. It should be noted that since the particularpermanent magnet used for this reed relay has very lar-ge resistance theeddy currents induced in the magnet are very small. In other words, themagnetic eld set up by the current to coil 13 is applied in fullstrength to achieve the desired effect and is not wasted in undesirablesecondary effects.

Once the reeds are closed the current through coil 13 may be cut off.The reeds are maintained in a lmake or closed position by the action ofthe magnetic field alone.

To open the reeds it is necessary to pass a current through coil 13 ofthe opposite pulse polarity or in the opposite direction. Thisdeactivating current through coil 13 must be sufficiently strong toreduce the magnetic field strength to a'value where the magnetic forceof attraction between the contacts 11b and 12b is less than themechanical bending moment in each reed forcin-g the reeds apart.However, it is imperative that the amount of current flowing throughcoil 13 does not set up a magnetic field strength to permanent magnet 14sufficient to cause the flux state in the permanent magnet to reverse.Once contact surfaces 11b and 12b have opened the current through coil13 may be shut off. When this occurs, the magnetic flux in permanentmagnet 14 returns to its initial state. This flux state, as mentionedpreviously is alone insuflicient to again close the reeds against theresistive mechanical force of bending induced in the contact springs.

It is important to note in this operation that due to the highretentivity of the plastic ferrite material used for the tubularpermanent magnet, the magnet does not act as a magnetic shield to themagnetizing field set up by the ow of current through the coil. On theother hand, the high retentivity of the material allows a sufficientmagnetizing lield to be set up in the opposite direction by passage ofcurrent of the reverse polarity without changing the direction ofmagnetization of the permanent magnet. It is this combination ofmagnetization characteristics coupled with the low eddy current lossesdue to the high resistivity of the material which makes this materialparticularly suited to the application, and which distinguishes thisinvention from the prior art.

What is claimed is:

1. A magnetically operated high speed switch structure comprising:

an energizing coil,

a pair of cantilevered contact reeds extending within an elongatedvitreous tube having Ian external surface and placed within said coil,said reeds activated in response to the energization of said coil;

and a plastic magnetic member, positioned directly on said externalsurface of said tube and in direct contact with said energizing coil,said member supporting said energizing coil and being in operativerelation therewith to maintain said reeds activated after deenergizationof said coil, yand to minimize the eddy currents generated by said coil.

2. An electromagnetic device comprising:

an energizing coil, f

a plurality of flexible contact reeds arranged in pairs and encapsulatedby ra hermetically sealed vitreous tube having two ends and an externalsurface, said tube being placed within said coil, one reed of said pairextending through one end of said tube and the other reed of said pairextending through the opposite end of said tube, the opposite ends ofsaid reeds extending within said tube and lying in an overlapping andnormally spaced apart relationship to each other, said reeds closing inresponse to the energization of said coil with current of one polarity,and restoring in response to the energization of said coil with currentof opposite polarity,

and a tubular shaped plastic magnetic member displaying both dielectricand permanent magnet properties positioned on said external surface ofsaid tube and in direct contact with said energizing coil, said membersupporting said energizing coil and being in operative relationtherewith to maintain said reeds closed after deenergization of saidcoil `and to minimize the eddy currents generated by said coil.

3. A magnetically operated high speed switch structure comprising: anenergizing coil, a pair of cantilevered contact reeds extendingwithin anelongated vitreous tube having an external surface and placed withinsaid coil, said reeds activated in response to the energization of saidcoil; and a plastic magnetic member, positioned directly on saidexternal surface of said tube and in direct contact with said energizingcoil, said member supporting said energizing coil and being in operativerelation therewith 5 6 to maintain said reeds closed afterdeenergization of said 3,024,392 3/1962 Baermann 317-159 coil, and tominimize the eddy currents generated by said 3,015,707 1/ 1962 Perreault200-87 COIL R f C t d OTHER REFERENCES e ences l e 5 The Ferreed-A NewSwitching Device, Bell Tech- UNITED STATES PATENTS nical Journal, v01.XXXIX, No. 1, January 1960, pp. 1l, 2,877,315 3/1959 oliver 20o-87 12and 19. 2,902,558 9/1959 Peek 200-87 2,978,556 4/1961 Lohs et al 200 87BERNARD A. GILHEANY, Primary Examiner.

2,999,915 9/ 1961 Pfleiderer et ai 200-87 10 R. N. ENVALL, AssistantExaminer.

1. A MAGNETICALLY OPERATED HIGH SPEED SWITCH STRUCTURE COMPRISING: ANENERGIZING COIL, A PAIR OF CANTILEVERED CONTACT REEDS EXTENDING WITHINAN ELONGATED VITREOUS TUBE HAVING AN EXTERNAL SURFACE AND PLACED WITHSAID COIL, SAID REEDS ACTIVATED IN RESPONSE TO THE ENERGIZATION OF SAIDCOIL; AND A PLASTIC MAGNETIC MEMBER, POSITIONED DIRECTLY ON SAIDEXTERNAL SURFACE OF SAID TUBE AND IN DIRECT CONTACT WITH SAID ENERGIZINGCOIL, SAID MEMBER SUPPORTING SAID ENERGIZING COIL AND BEING IN OPERATIVERELATION THEREWITH TO MAINTAIN SAID REEDS ACTIVATED AFTER DEENERGIZATIONOF SAID COIL, AND TO MINIMIZE THE EDDY CURRENTS GENERATED BY SAID COIL